Flow characterization of a microfluidic device to selectively and reliably apply reagents to a cellular network

Characterization of neuronal viability and network activity under microfluidic flow

BACKGROUND

Microfluidics technology has the potential to allow precise control of the temporal and spatial aspects of solute concentration, making it highly relevant for the study of volume transmission mechanisms in neural tissue. However, full utilization of this technology depends on understanding how microfluidic flow at the rates needed for rapid solution exchange affects neuronal viability and network activity.

NEW METHOD

We designed a tape-based pressurized microfluidic flow system that is simple to fabricate and can be attached to commercial microelectrode arrays. The device is multi-layered, allowing the inclusion of a porous polycarbonate membrane to isolate neuronal cultures from shear forces while maintaining diffusive exchange of solutes. We used this system to investigate how flow affected survival and spiking patterns of cultured hippocampal neurons.

RESULTS

Viability and network activity of the cultures were reduced in proportion to flow rate. However, shear reduction measures did not improve survival or spiking activity; media conditioning in conjunction with culture age proved to be the critical factors for network stability. Diffusion simulations indicate that dilution of a small molecule accounts for the deleterious effects of flow on neuronal cultures.

COMPARISON WITH EXISTING METHODS

This work establishes the experimental conditions for real time measurement of network activity during rapid solution exchange, using multi-layered chambers with reversible bonding that allow for reuse of microelectrode arrays.

CONCLUSIONS

With correct media conditioning, the microfluidic flow system allows drug delivery on a subsecond timescale without disruption of network activity or viability, enabling in vitro reproduction of volume transmission mechanisms.

Compartmentalized Microfluidic Platforms: The Unrivaled Breakthrough of In Vitro Tools for Neurobiological Research

Microfluidic technology has become a valuable tool to the scientific community, allowing researchers to study fine cellular mechanisms with higher variable control compared with conventional systems. It has evolved tremendously, and its applicability and flexibility made its usage grow exponentially and transversely to several research fields. This has been particularly noticeable in neuroscience research, where microfluidic platforms made it possible to address specific questions extending from axonal guidance, synapse formation, or axonal transport to the development of 3D models of the CNS to allow pharmacological testing and drug screening. Furthermore, the continuous upgrade of microfluidic platforms has allowed a deeper study of the communication occurring between different neuronal and glial cells or between neurons and other peripheral tissues, both in physiological and pathological conditions. Importantly, the evolution of microfluidic technology has always been accompanied by the development of new computational tools addressing data acquisition, analysis, and modeling.

Generating arbitrary chemical patterns for multipoint dosing of single cells

Living cells reside within anisotropic microenvironments that orchestrate a broad range of polarized responses through physical and chemical cues. To unravel how localized chemical signals influence complex behaviors, tools must be developed for establishing patterns of chemical gradients that vary over subcellular dimensions. Here, we present a strategy for addressing this critical need in which an arbitrary number of chemically distinct, subcellular dosing streams are created in real time within a microfluidic environment. In this approach, cells are cultured on a thin polymer membrane that serves as a barrier between the cell-culture environment and a reagent chamber containing multiple reagent species flowing in parallel under low Reynolds number conditions. Focal ablation of the membrane creates pores that allow solution to flow from desired regions within this reagent pattern into the cell-culture chamber, resulting in narrow, chemically distinct dosing streams. Unlike previous dosing strategies, this system provides the capacity to tailor arbitrary patterns of reagents on the fly to suit the geometry and orientation of specific cells.